This is a note to let you know that I've just added the patch titled crypto: drbg - prepare for more fine-grained tracking of seeding state to the 4.19-stable tree which can be found at: http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary The filename of the patch is: crypto-drbg-prepare-for-more-fine-grained-tracking-of-seeding-state.patch and it can be found in the queue-4.19 subdirectory. If you, or anyone else, feels it should not be added to the stable tree, please let <stable@xxxxxxxxxxxxxxx> know about it. >From foo@baz Fri Jun 17 08:58:56 AM CEST 2022 From: Nicolai Stange <nstange@xxxxxxx> Date: Thu, 2 Jun 2022 22:22:29 +0200 Subject: crypto: drbg - prepare for more fine-grained tracking of seeding state From: Nicolai Stange <nstange@xxxxxxx> commit ce8ce31b2c5c8b18667784b8c515650c65d57b4e upstream. There are two different randomness sources the DRBGs are getting seeded from, namely the jitterentropy source (if enabled) and get_random_bytes(). At initial DRBG seeding time during boot, the latter might not have collected sufficient entropy for seeding itself yet and thus, the DRBG implementation schedules a reseed work from a random_ready_callback once that has happened. This is particularly important for the !->pr DRBG instances, for which (almost) no further reseeds are getting triggered during their lifetime. Because collecting data from the jitterentropy source is a rather expensive operation, the aforementioned asynchronously scheduled reseed work restricts itself to get_random_bytes() only. That is, it in some sense amends the initial DRBG seed derived from jitterentropy output at full (estimated) entropy with fresh randomness obtained from get_random_bytes() once that has been seeded with sufficient entropy itself. With the advent of rng_is_initialized(), there is no real need for doing the reseed operation from an asynchronously scheduled work anymore and a subsequent patch will make it synchronous by moving it next to related logic already present in drbg_generate(). However, for tracking whether a full reseed including the jitterentropy source is required or a "partial" reseed involving only get_random_bytes() would be sufficient already, the boolean struct drbg_state's ->seeded member must become a tristate value. Prepare for this by introducing the new enum drbg_seed_state and change struct drbg_state's ->seeded member's type from bool to that type. For facilitating review, enum drbg_seed_state is made to only contain two members corresponding to the former ->seeded values of false and true resp. at this point: DRBG_SEED_STATE_UNSEEDED and DRBG_SEED_STATE_FULL. A third one for tracking the intermediate state of "seeded from jitterentropy only" will be introduced with a subsequent patch. There is no change in behaviour at this point. Signed-off-by: Nicolai Stange <nstange@xxxxxxx> Reviewed-by: Stephan Müller <smueller@xxxxxxxxxx> Signed-off-by: Herbert Xu <herbert@xxxxxxxxxxxxxxxxxxx> Signed-off-by: Jason A. Donenfeld <Jason@xxxxxxxxx> Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx> Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx> --- crypto/drbg.c | 19 ++++++++++--------- include/crypto/drbg.h | 7 ++++++- 2 files changed, 16 insertions(+), 10 deletions(-) --- a/crypto/drbg.c +++ b/crypto/drbg.c @@ -1042,7 +1042,7 @@ static inline int __drbg_seed(struct drb if (ret) return ret; - drbg->seeded = true; + drbg->seeded = DRBG_SEED_STATE_FULL; /* 10.1.1.2 / 10.1.1.3 step 5 */ drbg->reseed_ctr = 1; @@ -1087,14 +1087,14 @@ static void drbg_async_seed(struct work_ if (ret) goto unlock; - /* Set seeded to false so that if __drbg_seed fails the - * next generate call will trigger a reseed. + /* Reset ->seeded so that if __drbg_seed fails the next + * generate call will trigger a reseed. */ - drbg->seeded = false; + drbg->seeded = DRBG_SEED_STATE_UNSEEDED; __drbg_seed(drbg, &seedlist, true); - if (drbg->seeded) + if (drbg->seeded == DRBG_SEED_STATE_FULL) drbg->reseed_threshold = drbg_max_requests(drbg); unlock: @@ -1383,13 +1383,14 @@ static int drbg_generate(struct drbg_sta * here. The spec is a bit convoluted here, we make it simpler. */ if (drbg->reseed_threshold < drbg->reseed_ctr) - drbg->seeded = false; + drbg->seeded = DRBG_SEED_STATE_UNSEEDED; - if (drbg->pr || !drbg->seeded) { + if (drbg->pr || drbg->seeded == DRBG_SEED_STATE_UNSEEDED) { pr_devel("DRBG: reseeding before generation (prediction " "resistance: %s, state %s)\n", drbg->pr ? "true" : "false", - drbg->seeded ? "seeded" : "unseeded"); + (drbg->seeded == DRBG_SEED_STATE_FULL ? + "seeded" : "unseeded")); /* 9.3.1 steps 7.1 through 7.3 */ len = drbg_seed(drbg, addtl, true); if (len) @@ -1574,7 +1575,7 @@ static int drbg_instantiate(struct drbg_ if (!drbg->core) { drbg->core = &drbg_cores[coreref]; drbg->pr = pr; - drbg->seeded = false; + drbg->seeded = DRBG_SEED_STATE_UNSEEDED; drbg->reseed_threshold = drbg_max_requests(drbg); ret = drbg_alloc_state(drbg); --- a/include/crypto/drbg.h +++ b/include/crypto/drbg.h @@ -105,6 +105,11 @@ struct drbg_test_data { struct drbg_string *testentropy; /* TEST PARAMETER: test entropy */ }; +enum drbg_seed_state { + DRBG_SEED_STATE_UNSEEDED, + DRBG_SEED_STATE_FULL, +}; + struct drbg_state { struct mutex drbg_mutex; /* lock around DRBG */ unsigned char *V; /* internal state 10.1.1.1 1a) */ @@ -127,7 +132,7 @@ struct drbg_state { struct crypto_wait ctr_wait; /* CTR mode async wait obj */ struct scatterlist sg_in, sg_out; /* CTR mode SGLs */ - bool seeded; /* DRBG fully seeded? */ + enum drbg_seed_state seeded; /* DRBG fully seeded? */ bool pr; /* Prediction resistance enabled? */ bool fips_primed; /* Continuous test primed? */ unsigned char *prev; /* FIPS 140-2 continuous test value */ Patches currently in stable-queue which might be from nstange@xxxxxxx are queue-4.19/crypto-drbg-prepare-for-more-fine-grained-tracking-of-seeding-state.patch queue-4.19/crypto-drbg-track-whether-drbg-was-seeded-with-rng_is_initialized.patch queue-4.19/crypto-drbg-make-reseeding-from-get_random_bytes-synchronous.patch queue-4.19/crypto-drbg-move-dynamic-reseed_threshold-adjustments-to-__drbg_seed.patch